Add a device node for the ROHM BD9571MWV PMIC.

This was based on the example in the DT binding documentation, but using
IRQ0 instead of a GPIO interrupt, as that matches the schematics, and
because INTC-EX is a simpler block.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>